Gas Flow Distribution in Pelletizing Shaft Furnace

Through thermal test, cold state experiment, analysis and simulation of thermal process, the gas flow distribution in pelletizing shaft furnace （PSF） was discussed. The results show that there are five flowing trends among them, the downward roasting gas and the upward cooling gas are the most unsteady, which influence flow distribution greatly. Among the operating parameters, the ratio of inflow is a key factor affecting the flow distribution. The roasting and cooling gases will entirely flow into the roasting zone and internal vertical air channels （IVAC）, respectively, if the ratio of inflow is critical. From such a critical operating condition increasing roasting gas flow or decreasing cooling gas flow, the roasting gas starts flowing downwards so as to enter the inside of IVAC the greater the ratio of inflow, the larger the downward flowrate. Among constructional parameters, the width of roasting zone b1, width of IVAC b2 and width of cooling zone b3, and the height of roasting zone h1, height of soaking zone h2 and height of cooling zone hs are the main factors affecting flow distribution. In case the ratio of b2/b3, or h3/h2, or h1/h2 is increased, the upward cooling gas tends to decrease while the downward roasting gas tends to increase with a gradual decrease in the ratio of inflow.

Fundamental Study on New Method of Reducing Iron Ore-Coal Pellet in Cocurrent Shaft Furnace

Based on the laboratory experiment of reducing iron ore-coal pellet in oxidizing atmosphere,a new self-heating reduction method of iron ore-coal pellet in the cocurrent shaft furnace(CSF) has been developed.In this process,the pellets and preheated oxygen-enriched air enter the shaft furnace through its top and descend cocurrently in the furnace.Most of the heat required for rising temperature and endothermic reduction of descending pellets is provided by the way that the descending air burns the volatile from pellets and CO from the reduction of iron oxide in pellets.The reduced pellets and high temperature gas are discharged from the lower part.The sensible heat and chemical energy of the off-gas are used to heat the oxygen-enriched air in stove.This process is applicable to the direct reduction of iron pellets and prereduction of iron pellets in smelting reduction with iron bath.

Moving behavior of pellets in a pellet shaft furnace

The downward moving behavior of pellets in a 8 m2 pellet shaft furnace with an internal vertical air channel and a drying bed was studied by means of a visualized model(1-15) and a top model(1-1).The visualized model experiment shows that the downward movement of pellets can be regarded as plug flow approximately inside the furnace except for the lower region of cooling zone due to the influence of the drained hopper.The top model experiment reveals that the pellet sizes increase along the moving direction because of the percolation phenomenon,which results in a decrease of the resistance coefficient and an increase of the gas flow rate from the furnace wall toward the furnace center.

Reduction of Carbon-bearing Pellets of Oolitic Hematite in a Shaft Furnace

When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each other at high temperatures;and the separation of phosphorus from iron is difficult.To solve these problems,experiments were conducted on oolitic hematite reduction in a resistance furnace and semi-industrial test shaft furnace.The results showed that the metallization rate reached 90% or greater under the conditions of a reduction temperature of 1 150℃,an atmosphere of simulated flue gas,and a reduction time between 1.5and 2.0h.The problem of high-temperature bonding among pellets can be solved by increasing the strength of the pellets,coating their surface with a surface transfer agent and maintaining an even temperature inside the shaft furnace.The basicity of the ore blend exerted no obvious effect on the magnetic concentrate and phosphorus content.The phosphorus content in the magnetic concentrate can be further reduced by improving the grinding capacity of the ball mills used in the experiments.On the basis of the experimental results related to oolitic hematite reduction with carbon-bearing pellets in a shaft furnace,the experimental requirements were satisfied with an average 88.27%total Fe content and 0.581% P content in the pellets.

Exploring a new path of green and efficient utilization of sinter return fine to produce composite pellets

Efficient utilization of sinter return fine is an important measure to reduce cost,increase efficiency,save energy and reduce emission.A new path of green and efficient utilization of return fine was proposed to produce composite pellets.The metallurgical properties of composite pellets under the condition of hydrogen-rich blast furnace were studied.The experimental results indicate that the coated concentrate was consolidated for the composite pellets through normal Fe_(2)O_(3) recrystallization.Near the surface of core return fine,the liquid phase formed due to its low-melting point,assimilated the adjacent concentrate,and then consolidated with the temperature decreasing.Compared with regular pellets,the com-pressive strength and reduction swelling index of composite pellets were decreased,but the reducibility index and softening-melting properties were improved.In addition,the reduction degradation index of composite pellets was sig-nificantly higher than that of sinter.Therefore,adding composite pellets was conducive to indirect reduction in blast furnace,reducing fuel ratio and improving production efficiency.According to the effect of the roasting system on the metallurgical properties,the roasting temperature and time were determined as 1250℃and 30 min,respectively.The composite pellets can be produced under the traditional pelletizing process.

Analysis of Gas Thermodynamic Utilization and Reaction Kinetic Mechanism in Shaft Furnace

The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways, i.e. thermodynamics and kinetics, the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment. The results showed that the gas utilization increased with the rise of temperature when xH2/xco≥1 and with the increase of xco/（xH2 ＋xco） when temperature is less than 1073 K. The water-gas shift reaction restrains efficient utilization of gas, particularly in high tem- perature and hydrogen-rich gas. The gas utilization dropped with increase of carburization quantity of direct reduction iron （DRI） and oxygen potential of atmosphere. With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased. At 100% Hz atmosphere, the interfacial chemical reaction is the dominant reaction re- stricted step. For the H2-CO mixture atmosphere, the reduction process is controlled by both interfacial chemical reaction and internal diffusion

Effects of Temperature and Atmosphere on Pellets Reduction Swelling Index

After taking into account the conditions of the domestic iron resources and the non-coking coal resources, the process of coal gasification-shaft furnace is an effective way to develop direct reduction iron in China. The following tasks are very critical to choose suitable process of shaft furnace and gasification, including the production of oxidized pellets with excellent comprehensive properties as well as the study of the reaction behavior and mechanism of swelling. The results showed that the oxidized pellets of using domestic magnetic iron concentrate as raw materials have favorable comprehensive properties, including higher mechanical strength both before and after reduction, faster reduction rate and lower reduction swelling index (RSI). All of these properties can meet the shaft furnace yielding requirement. When the temperature was below 1 223 K, the pellets′ RSI was lower than 20%. With increasing of the content of H2 in atmosphere, the pellets reaction rate accelerated, crushing strength enhanced and RSI decreased. The RSI dropped to 10.26% at 1 323 K in 100% H2 atmosphere, and it is up to 39.88% in 100% CO atmosphere. The iron grains mainly presented in platelike when pellets were reduced by H2, however, in CO atmosphere the iron grains were precipitated in flocculent. The whisker shape of iron grains and heating effects of reduction reaction are the major factors leading to the poor pellets strength and increase of RSI. Appropriately controlling the temperature and increasing the ratio of H2 to CO in atmosphere are good for dropping the RSI.

Kinetics of Oxidation Reaction for Magnetite Pellets

An experiment for the oxidation process of single magnetite pellet and theoretical analysis based on modi lied unreacted core shrinking （MUCS） model were carried out, and the controlling mechanisms of the initial and de veloping reactions were examined, respectively. From the study of the initial reaction, it was found that the chemical reaction of surface is the controlling step of the overall reaction when the temperature is up to about 750 K, while the mass transfer through the gaseous boundary layer dominates the reaction rate when the temperature is above 750 K. As the reaction developing within the pellet, the mass transfer through the produced layer becomes the controlling step. In addition, the effects of reaction conditions （such as oxygen concentration, temperature） on the fractional oxidation of magnetite pellet were determined.

Influence of basicity on metallurgical performances of fired super high-grade magnetite pellets in hydrogen-rich gases

The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.

鞍山式竖炉排矿系统自动控制研究

鞍山式焙烧竖炉矿石在炉膛内随排矿系统间歇式运动,停止搬出时间越长,矿石在炉膛内受热、还原不均的问题越严重,由此探索自动控制竖炉搬出周期对焙烧矿指标的影响,研究不同搬出周期模式下的焙烧矿产、质量变化,确定最优的竖炉搬出周期。

还原磁化焙烧竖炉冷却系统研究

某氧化铁矿石属于难选铁矿石,磁化焙烧工艺是处理此类铁矿石最有效的方法之一。竖炉磁化焙烧工艺加工成本相对较高,其中竖炉冷却系统是竖炉加工成本的重要组成部分,通过对竖炉冷却系统冷却水速、水箱梁水垢、水箱梁冷却水量等方面的研究,探索高效、节能的竖炉冷却系统.

张宣科技氢基竖炉开炉操作

对张宣科技氢基竖炉开炉操作实践进行了总结。氢基竖炉采用焦炉煤气COG作为气源,开炉前,重点保证高品质球团矿稳定供应、系统分级试压检漏消除漏点、建立塔器液位及循环;2023年5月10日点火开炉,开炉过程中,主要做好启动COG压缩机、加热炉点火升温、装排料、引送高压COG、并入CO_(2)脱除系统、启用喷氧系统等工作,并进行加风强化和控制DRI化学成分操作。5月20-21日,DRI含C量下降至3%左右,达到炼钢电炉的配加要求,且DRI金属化率提升至94%以上,达到设计水平。

张宣科技氢基竖炉生产工艺特点

张宣科技氢基竖炉在全球率先采用焦炉煤气COG生产直接还原铁DRI,设计矿比1.350,DRI含C<3.0%、金属化率≥92%,COG单耗低于650m^(3)/t,利用系数3.50t(m^(3).d),年产量55万t/a。以宣钢焦化厂副产品COG作为气源,还原气先经加热炉一次加热至920~960℃,再经燃烧室喷氧二次加热至1000~1050℃,然后被送入竖炉内还原高品质球团矿,生产的DRI经冷却,低于60℃后排出竖炉冷却器。氢基竖炉生产工艺主要具有H_(2)直接还原为主、工艺流程简单、原料适应性强及产品多样化、氢能利用率高等特点,与相同产量的高炉相比,CO_(2)排放量减少70%,粉尘排放量减少90%,SO_(2)排放减少50%。

氢基竖炉直接还原提产降耗生产实践

张宣科技氢冶金技术HyMEX以H 2含量60%的焦炉煤气为气源,成为全球首创的“焦炉煤气零重整竖炉直接还原”工艺技术,该技术的核心是焦炉煤气零重整工艺,入炉工艺气H 2含量超过以天然气为气源的Midrex和HYL/Energiron工艺,使气基直接还原转变成以氢为主的氢基直接还原,推动了我国钢铁行业由“碳冶金”向“氢冶金”转变。为提高氢基竖炉产量,降低能耗,从生产过程中出现的问题和影响球团矿还原的各个环节及能量利用效率等角度出发,探究了提产降耗措施。通过降低球团矿成分标准偏差、改善球团矿粒级组成、改善球团矿涂覆效果,提升球团质量;将工艺气入竖炉温度提高到1030℃;通过降低还原循环气体氧化度、尾气分流、补充焦炉煤气、增加加湿操作,优化调控竖炉内还原气氛;提高尾气利用率及作业率等措施,实现了提产300 t/d、焦炉煤气单耗降低133 Nm^(3)/h的目标,为后续进一步提产降耗奠定了坚实的基础。

国内铁精矿粉制备气基竖炉专用高品位球团矿

随着钢铁行业碳减排压力的增大,气基竖炉-电炉短流程工艺的应用可有效降低碳排放,高品位球团矿作为气基竖炉冶炼原料,其制备过程及特性研究尤为重要。本文使用国内6种不同的铁精矿粉制备高品位球团矿,阐述了球团矿的制备过程,研究了球团矿的性能。结果表明:最佳配矿方案为70%矿粉1+30%矿粉2,此配矿生球抗压强度为11 N/球,落下强度为3.1次/球;配矿球团矿w(FeO)为1.00%,铁精矿成品球团矿w(FeO)≥0.59%,亚铁含量较低,氧化充分,球团矿质量受控;配矿成品球团矿的抗压强度达到3031 N/球,铁精矿成品球团矿抗压强度≥3200 N/球,质量满足生产要求;还原性指数≥4.000,还原膨胀指数≥7.45%,LTD_(+6.3)≥97.00%,LTD_(UP)均为100%,还原性能良好。通过对现有设备的技术改造及配矿方案的优化,使用国内铁精矿粉可以制备出满足气基竖炉生产标准的优质高品位球团矿。

氢基竖炉用球团生产工艺优化

竖炉用高质量球团是当前研究热点,回转窑球团产线中链篦机-回转窑-环冷机各部温度优化控制是提高球团产质水平的重要环节。介绍了链篦机-回转窑-环冷机设备优化过程以及造球工艺优化措施。首先在生产工序中缩短了干燥段,延长了预热段,同时改善了环冷机热量流通,为更好的氧化焙烧奠定了基础;在造球流程改造中,将造球盘角度统一调整为46°,旋转刮刀的转速均调整为10 r/min,旋转刮刀与底衬的距离调整为30~40 mm,造球盘落料点较之前向盘内延伸100 mm,小皮带下料点到边板距离达到43 cm,最终成球效果得到明显提升。对比工艺改进前后生产球团,其还原性能有所提升,还原膨胀及低温还原粉化指数均有所改善,其还原性能有所提升,还原膨胀率有所降低,其中1号球团还原膨胀率由12.34%降低到了7.82%,低温还原粉化指数改善明显,LTD+6.3均提高了20%左右。同时造球工艺优化为我国氢基竖炉用优质铁精矿球团提供了帮助。

程潮磁铁精矿磁悬浮精选机提精降杂试验研究

为使程潮选矿厂的精矿球团满足氢基竖炉对品质的要求,在对现场精矿进行详细分析的基础上,采用悬浮磁精选机进行了精选试验。结果表明,试样不磨矿,直接进行2段悬浮磁精选机精选,可获得品位为68.63%、回收率为96.51%的精矿,并产生品位为36.11%、回收率为3.49%的精选尾矿;试样在磨矿细度为-37μm占75%、上升水流为12 L/min、磁场强度为8.8 kA/m情况下进行2段悬浮磁精选机精选,可获得品位为68.71%、回收率为98.81%的精矿,品位为18.38%的尾矿经磁选管再选可降至14.62%,获得的品位为51.06%、流程回收率为0.34%的低品位精矿可返回再磨作业。虽然2个流程均能获得符合目标要求的精矿,但有预先磨矿的流程不仅精矿品位略高,且回收率高2.3个百分点,因此,该流程有一定的优越性。

提高竖炉球团台时产量生产与实践

球团矿由于具有品位高、强度好、易还原、粒度均匀、透气性好等优点,提高炼铁铁水产量具有积极的促进作用。酒钢炼铁厂球团竖炉自投产以来,不断地进行配矿研究、设备改造和操作方法改进,使竖炉产质量不断改善,利用系数不断提高,大大缓解了高炉对球团产能的压力。

球团竖炉热工过程解析与模拟

在现场热工测试基础上 ,对导风墙—干燥床式球团竖炉的干燥、预热、焙烧与冷却过程进行解析 ,建立了导风墙—干燥床式球团竖炉热工过程的数学模型 ,并且对生产条件下的济钢 2号球团竖炉进行了模拟 ,结果表明 :计算值与模拟值基本相符 ,干燥床面积、焙烧风及冷却风与球团热流比、焙烧带氧含量是竖炉增产的关键因素 ,焙烧带氧含量须保证在 5

球团竖炉内气流运动规律的实验研究

根据相似原理建立'导风墙-烘干床'式球团竖炉冷态模型实验台,根据实验数据绘制流网图,从而判断竖炉内气流分布状况,得到竖炉操作参数对炉内气流运动的影响规律:竖炉结构参数一定,流入风量比k决定着气流分布:当流入风量比等于临界风量比时,焙烧风和冷却风分别全部流入焙烧带和导风墙内,此时,竖炉处于临界工况;由临界工况开始增加焙烧风或减小冷却风,则开始有焙烧风下行进入导风墙,且k愈大,下行的焙烧风量愈大;由临界工况开始减小焙烧风或增加冷却风,则开始有冷却风上行进入焙烧带,且k愈小,上行的冷却风量愈大;上行冷却风和下行焙烧风中只有一种情况发生或均不发生·